Generally, semi-dynamic flip-flops have two operation modes. When the semi-dynamic flip-flops transitions between the two operation modes, keep circuits are used for reducing the likelihood, or possibly preventing, signal fighting. However, when the semi-dynamic flip-flops adopt the keep circuits, there are trade-offs between operating speed and noise. In other words, semi-dynamic flip-flops are not easily applicable to applications that require a high speed and relatively less noise.